The Research On Implementation Of Digitized Ultrasonic Diagnostic Equipment Based On FPGA

Digitized ultrasonic diagnostic equipments are widely used in medical diagnostics. The tendency of the development of this kind of medical instruments is to be totally digitized. Although many of the ultrasonic imaging instruments have been made by digital technology, but we can draw a conclusion that the modern VLSI and EDA technique have not been used efficiently. With the development of modern electron and information technology, the PLD has been applied to some fields such like digital communication or phase array radar, which are tightly related with B-scan or Doppler echo imaging. In study of modern ultrasonic imaging methods, we introduced the common infrastructure and module functions of digitized ultrasonic imaging instruments at first. Then we also introduced modern FPGA and EDA design techniques. In study of B-mode ultrasonic imaging equipment, we have discussed, in detail, some key techniques and realization method of totally digitalized multi-beam forming. We have designed an in-chip high speed asynchronous FIFO to reduce the sample rate, the simulation results shows it can be used to reduce system resource cost and it has very low access time. Orthogonal detection can give us both the amplitude information for gray-scale imaging and phase shift information for doppler spectrum analysis. We have designed and implemented a numeric controlled oscillator (NCO) based on direct digital synthesizer (DDS) theory, which can give a pair of quadrature signals with well-balanced amplitude and phase. The implementation circuit inside a single FPGA chip of this plan was simple and cheap. And, the frequency of the output waves can be numeric controlled with high precision. This can be used as a compensation method to shift the center frequency of the beam receiver synchronously with the shifting of the center frequency of broadband echo signals lead by acoustic attenuation in tissue. We also presented an application of FPGA to electronic phased focusing and scan control sub-system for electronic linear scanning, B-mode ultrasonic diagnostic equipment. We designed the driven-pulse generator module whose focusing delay, pulse width, pulse repetition frequency can be dynamically controlled by pre-computed codes. Also we achieved linear scanning control and probe impulse control and function code storage and other system functions both in a signal FPGA chip. Both the function simulation and timing simulation results of this sub-system show that it lays a good foundation on building high speed, high precision, fully digitalized, highly integrated modern medical ultrasonic diagnostic equipments. This paper will help to the researching and producing process. It is fresh air to the biomedical electronics, medical instrument, and medicine ultrasonic.